Indri (Indri Indri) songs can be heard from kilometers away and serve to defend a pair’s territory, advertise the position of the group within the territory, and maintain contact between group members even when far apart. 

[Photo, recording, and caption by Meredith Lutz]

Torti, V., Gamba, M., Rabemananjara, Z. H., & Giacoma, C. (2013). The songs of the indris (Mammalia: Primates: Indridae): contextual variation in the long-distance calls of a lemur. Italian Journal of Zoology, 80(4), 596-607.